This invention generally relates to an electrical connector and method of making an electrical connection and, more particularly, to an electrical connector that can be installed very quickly and reliably maintains a retention force on the conductor during long periods of operation.
It is frequently necessary to join electrical conductor cables together, especially in utility applications, and then pass high current and high voltage across the connection. The connectors used are required to be strong, and oftentimes are subjected to high temperature, excessive vibrations and other adverse operating conditions. In addition, the installation of such connectors often must take place in the field or in awkward or crowded areas where a quick and easy installation is favored.
It is generally desired to maintain the electrical resistance across a connector device at as low a value as practical. Resistance is normally kept at a level equal to or lower than an equivalent unbroken conductor. It is also important to maintain the resistance value in a stable manner over a variety of adverse operating conditions for a long period of time. Other important considerations for such connections are the mechanical strength of the connection, the time taken to make the connection and the amount of material used in the connector device.
One prior art device commonly used for this type of electrical connection is a cap and body connector which is held together by a nut and bolt arrangement. The conductors are first placed between the cap and body. The bolt then is placed through an opening in the cap and body and the nut is screwed on the bolt and tightened down onto the cap. Tightening is continued to a predetermined degree to compress the cap and body onto the cables. As the compression force is increased on the cables during the tightening process, the electrical resistance across the connection is lowered to a level determined by the geometry of the device. Devices in the prior art which disclose connectors of this type are described in U.S. Pat. No. 3,248,684 to Hubbard et al and in German Pat. No. 193,455 to Schrauben.
One problem with the nut and bolt arrangement is that during operation of the electrical connector, heat build-up can cause an expansion of the various parts of the connector and a relaxation of the retention force placed on the conductors thereby. Such relaxation can be sufficient to cause an irreversible loosening of the connector. This, in turn, causes the electrical resistance to increase and the connector can lose efficiency. The possibility of this relaxation occurring, which may also be caused by vibration as well as other factors, is heighted when different materials are used within the connector. For instance, it is common to use aluminum caps and bodies that are held together with steel nuts and bolts. In addition, the torque applied to the nut during the original tightening process may vary from connector to connector because of hand tightening, different installers etc., further reducing the assurance that such connectors will operate in the manner intended.
Another commonly used prior art device is the wedge-type connector for joining conductors. This two-piece device has an outer shell and an inner wedge. The shell is generally made to taper in conformance with the angle of the wedge. Cables are placed in the shell, and the wedge placed therebetween and driven into the cable/shell arrangement for a snug fit. This type of device uses a relatively large amount of material and is not an easy one to assemble, especially in the field or in cramped locations. It is also quite limited in terms of the range of conductor sizes that each connector can accommodate. This type of connector is disclosed in U.S. Pat. No. 3,235,944 to Broske et al.
Still another type of electrical wiring connector, usually used for joining much smaller conductors than those employed in the utility field, is made of nonconductive, semi-flexible plastic material. This prior art device makes a connection between two insulated wires without the necessity of first removing the insulation from the wires. The device is made of two identical halves, each half having a stud and a hole to receive the stud. The studs have concentric ribs which snap into the holes when the two halve are placed together face-to-face. Because of the resilience of the material, the studs can be forced into the holes until they pop out the other side allowing the ribs to assume their original shape and hook over the outer surface of the connector. Such connectors have the drawbacks of relatively low retention force because of the resiliency of the material used and possible instability due to high temperatures. They also require special conductors embedded therein to pass the current. U.S. Pat. No. 3,115,541 issued to Hanner et al discloses a connector of this type.
Electrical terminals are also known which have connector screw structures attached to a terminal block by a pin pressed into the block. U.S. Pat. No. 3,135,572 to Curtis et al discloses such a terminal. In addition, general use mechanical fasteners are known which have a plurality of concentric lands on their shafts which, as they are being driven into the material being fastened, urge the material to flow into the spaced regions between the lands. A mechanical fastener of this type is disclosed in U.S. Pat. No. 3,661,406 to Mele.
Accordingly, it is an object of the present invention to provide an improved connector device which reliably maintains a high retention force on the conductors.
It is another object of the invention to provide an improved connector device which, upon assembly, places a uniform retention force on the conductors.
It is another object of the invention to provide an electrical connector which is relatively quick and easy to install.
It is another object of th invention to provide an electrical connector which maintains a relatively low connector resistance level under adverse operating conditions over a long duration.
It is another object of the invention to provide an electrical connector device which uses less materials for the retention force placed on the connector.
It is another object of the invention to provide an electrical connector for utility applications which is smaller than the prior art device.
It is another object of the invention to provide a strong electrical connector device.
It is another object of the invention to provide an electrical connector device that can accommodate a relatively large range of conductor sizes.